Known devices for applying medical treatment to a local part in a living body include instruments for medical treatment in which an injection needle is disposed in a catheter so as to be forwardly and rearwardly movable, with the catheter being inserted into the local part or into the vicinity of the local part, and a drug solution is injected via a distal portion of the injection needle into the local part.
As an example, Japanese Application Publication No. 2001-299927 discloses a drug solution injection catheter in which an injection needle projects through a circumferential wall of a catheter inserted in a blood vessel so as to inject a drug solution. In using this catheter, the catheter is first inserted into the inside of the blood vessel, and an expandable-and-contractible balloon section disposed at a distal portion of a shaft section of an elongated flexible tube body is inflated to make close contact with the blood vessel wall, thereby setting and holding the shaft section in a fixed state. Thereafter, the injection needle is projected via a needle hole of the catheter to allow puncture of a cardiac muscle layer at a lesion to inject a predetermined drug solution and thereby perform medical treatment.
The catheter described above exhibits the following difficulty. In a fixed setting state wherein the balloon section is inflated within a blood vessel, an attempt to make the injection needle puncture a desired part may result in the injection needle moving in a playing manner due to the load of a puncture reaction force generated in this instance, thus leading to an error in the puncturing position. As a result, the response of the injection needle to an operation on the proximal side may be worsened, hampering an accurate drug solution injection.
In particular, in a medical treatment applied to an area of the brain, it is necessary to minimize the damage to the brain tissue as the injection needle is handled. It is desirable for the injection needle to be able to puncture a predetermined part of brain tissue without damaging the brain tissue.